Experimental absorptance data are given for atmospheres of pure ammonia and for mixtures of ammonia and nitrogen at wavelengths between 20 and 35 µ. The wavelength interval is subdivided into five regions and the total absorptance is tabulated as a function of ammonia pressure and nitrogen pressure for each region. The average absorptance for each region is plotted as a function of the parameter <i>U= WP</i>*, in which <i>W</i> is the ammonia concentration and <i>P</i>* is an effective pressure. This effective pressure is the sum of the total pressure and the ammonia partial pressure multiplied by a self-broadening factor. A single absorptance function fits each region, indicating that the absorption is in the strong line region for the gas pressures used. This absorptance function does not agree with the strong-line limit of either the Goody or Elsasser models of band absorptance.
THOMAS E. WALSH, "Infrared Absorptance of Ammonia—20 to 35 Microns," J. Opt. Soc. Am. 59, 261-267 (1969)